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Space qualification of Leti's Absolute Scalar Magnetometer

November 29, 2010 | Jean-Michel Léger | 222901853

Jean-Michel Léger of CEA-Leti outlines details of the SWARM space mission's key research instruments – the absolute scalar magnetometer (ASM).

As the European Space Agency (ESA) moves toward a possible July 2012 launch date for its SWARM space mission to study the earth’s magnetic field, scientists here at CEA-Leti are well on the way to delivering one of the mission’s key research instruments – the absolute scalar magnetometer (ASM).

Developed by Leti (Laboratory for Electronic and Information Technologies of the French Atomic Energy Commission) for airborn magnetic anomaly detection applications, the absolute scalar magnetometer was selected in 2005 by the European Space Agency (ESA) as the magnetic payload reference instrument for SWARM.

This mission’s objectives are to improve our understanding of the Earth’s magnetic-field structure, evolution and interaction with the solar wind. To achieve this, three satellites on different orbits will be operated over a four-year period. This constellation operation represents a significant improvement over previous single-satellite missions dedicated to the Earth’s magnetic field study, such as Denmark’s 1999 Ørsted mission and Germany’s 2000 Champ mission, for which Leti and CNES (French government space agency) developed an earlier technology based on nuclear magnetic resonance (NMR) magnetometers. SWARM will provide direct benefits for many different practical applications such as monitoring space weather and radiation hazards, and navigation and resource management.

In this context, the ASM will be used to provide absolute scalar in-flight calibration of the mission’s vector-field magnetometer, developed by the Danish National Space Center. As it is essential to fulfill the mission’s scientific objectives, special care has been devoted to ensure both its reliability and its availability, and a dedicated qualification program has been defined and conducted to raise the instrument to Technology Readiness Level (TRL) 8 before the flight models’ delivery to ESA. This has been achieved thanks to a close partnership between Leti, which focused on the instrument design and characterization, and CNES, which provided expertise on both development methodology and space-applications specificities.

The first step consisted of an in-depth analysis of the existing prototype, which in turn led to a complete revision of the detailed design. Standard components were replaced whenever possible by ones selected from the European Space Components Coordination Qualified Parts List (ESCC-QPL). As for the digital electronics, an ASIC based on the Atmel Rad Tolerant 0.35µm Sea of Gates MH1RT space-qualified technology was developed after an initial design validation on a field-programmable gate array (FPGA). Thanks to a very thorough testing at each production step, it was fully operational on its very first release.

On the other hand, since the instrument comprises several very advanced components that were only available either as commercial off-the-shelf (COTS) components or existed only as laboratory prototypes, a complementary qualification campaign was mandatory. In particular, the piezoelectric motor and the 1.08µm laser, plus all the related optics components, had to be submitted to aging and environment studies to demonstrate their capacity to meet the mission’s requirements.

In parallel, once enough confidence had been gained on the various parts, but before the actual components-qualification completion, an engineering-qualification model and a protoflight model were successively manufactured and qualified in combined metrological and environment tests (radiation hardness, mechanical, thermal vacuum and electromagnetic compatibility tests).

All these tests have now been completed and the laser, which was the most delicate component, was declared “space qualified” a few weeks ago, making it the very first fiber laser to achieve that status. We expect to deliver the first actual flight models by the end of this year, and the remaining ones in early 2011.

To access the instrument description and infrastructure (in PDF format), click here.

Arctic test flight
Meanwhile, this magnetometer technology has also proven its viability in extremely demanding conditions. As part of French explorer Jean-Louis Etienne’s Generali Arctic Observer mission to cross the Arctic Circle by balloon earlier this year, a prototype of the ASM system collected magnetic data during a five-day balloon flight that traveled more than 3,000 kilometers above the Arctic Ocean and the frozen tundra of Siberia. Despite a strong magnetic storm that reduced the value of the collected data, CEA-Leti’s magnetometer technology worked as expected and accomplished its mission with flying colors.

About the author:
Jean-Michel Léger is Space Applications Program Manager at the Grenoble-based CEA-Leti, a French research institute focused on micro- and nanotechnologies and their applications.

Image Gallery

Artist view of the Swarm constellation in orbit, thanks to which a significant step forward is expected in the identification of the various sources contributing to the Earth’s magnetic field structure

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